Weight and space requirements of portable computers have been constantly decreasing over the years. U.S. Pat. Nos. 5,199,888 and 5,208,736 and patent application Ser. No. 08/188,488 filed Jan. 28, 1994, all assigned to the assignee of the present invention and incorporated herein by reference for all purposes, are examples of notebook computers.
The combination of a cellular telephone with these portable computers has been attempted in the past using separate cellular telephones connected to modems in notebook computers, such as shown in FIG. 3 of WO92/10047 and the Toshiba "T24D/X" device used with the portable computers of Toshiba of Irvine, Calif.
Cellular telephones have also been fabricated integrally with the portable computers. Some of those cellular notebook computers include retractable omnidirectional antennas in the liquid crystal display or LCD section of the computer, such as shown in FIG. 6 of U.S. Pat. No. 4,972,457 and FIGS. 3 and 4 of U.S. Pat. No. 4,991,197. Additionally, Intelligence Technology Corporation of Dallas, Tex. offered the "ITC 286 CAT" cellular notebook computer. The "ITC 286 CAT" computer also has a retractable omnidirectional antenna coming out of the display section.
Intelligence Technology Corporation later introduced a cellular notebook computer with a rail on the back side of the display section to slidably receive a Motorola "DYNATAC" cellular phone. Also, GRID Systems Corporation of Fremont, Calif. and PowerTek Industries, Inc of Englewood, Colo. jointly introduced a cellular notebook computer with a proprietary error-correcting feature to increase data-transfer speeds. The cellular telephone of the GRID/PowerTek cellular notebook computer could be separated from the notebook computer and used alone.
One problem with combining a cellular phone with a notebook computer was the undesirable effect of electromagnetic interference power or EMI power emitted by the computer on a cellular phone. The net peak EMI power from notebook computers have been measured at -73 dBm for a Compaq LTE 386s/20 and -90 dBm for an Olivetti Quaderno.
Since the sensitivity of a cellular phone is approximately -110 dBm, EMI power hitting the antenna greater than -110 dBm could prevent the cellular phone from working properly in combination with the computer.
Even if the EMI power is less than the cellular phone sensitivity, the bit error rate of the transmission has been found to increase. Even with the error-correcting features, such as MNP10 or SPCL, the user would experience a slowing down of the transfer speed.
Therefore, with antennas, similar to the "ITC 286 CAT" cellular notebook computer and the cellular notebook computers disclosed in U.S. Pat. Nos. 4,972,457 and 4,991,197, which are incorporated herein for all purposes, positioned adjacent the display section, significant EMI power is picked up from the logic module of the computer.
Other antenna devices now being used include an integral loop antenna which, though inexpensive and directional, is situated near the EMI power sources in the computer. Also, an omnidirectional vertical dipole antenna has been used. Other examples of antennas used with a notebook include U.S. Pat. No. 5,138,328 that discloses the use of dual printed circuit board based antennas located in the display section to provide RF modem capability for a notebook computer.
In summary, the above cellular notebook computers have been undesirable because the antennas are omnidirectional and/or too close to the EMI power produced by the logic module in the computer. Therefore, it would be desirable to provide a directional antenna system that could be remotely positioned from the EMI power emitted by the computer. It would also be desirable if this remote directional antenna system would provide these enhanced operational characteristics with minimum additional space and weight to the notebook computer.